17557-6003-RU-00Revised

TRW PLASMA WAVE EXPERIMENT

I FOR THE IMP-H MISSION

r

by

P. F. Virobik and F. L. Scarf

TRW Systems GroupOne Space Park

Redondo Beach, California 902780

0 October 1973

o Final Report for Periodn mFebruary 1971 - February 1973

g o(Revised)

EPrepared for

ri r, Goddard Space Flight Centerrc o Greenbelt, Maryland 20771co 0

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TRWSYMEMS GROUP

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TECHNICAL REPORT STANDARD TITLE PAGE

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle 5. Report ote

TRW PLASMA WAVE EXPERIMENT FOR THE IMP-H October 1973MISSION (Revised) 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

P. F. Virobik and F. L. Scarf 17557-6003-RU-009. Performing Organization Name and Address 10. Work Uni Noa.

TRW Systems Group 11. Contract or Grant No.

One Space Park NAS 5-11384Redondo Beach, Cal ifornia 90278 13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address Revised Final Report forPeriod February 1971 -

NASA Goddard Space Flight Center February 1973Greenbel t, Maryland 20771 14. Sponsoring Agency Code

701. 115. Supplementary Notes

16.Abstract The IMP-H Plasma Wave Experiment is designed to extend know-ledge of wave-particle interactions in the disturbed cislunar region,the distant geomagnetic tail, the upstream solar wind, and the flanksof the magnetosheath-shock interface. We expect to identify plasmainstabilities, study particle acceleration and heating at collisionlessshocks and other discontinuities, analyze turbulent conductivity andfield line merging, and provide new information on dissipation proces-ses for suprathermal particles.

Instrumentation for the plasma wave experiment is designed tomeasure local electric and magnetic field oscillations over the fre-quency range 10 Hz to 100 kHz. A 24" electric dipole, a 7" diameterair core search coil, and the associated preamplifiers are mounted ona spacecraft counterweight boom. The frequency range of 10 Hz to 100kHz for both E and B is processed using an eight-channel spectrum ana-lyzer located in the instrument main-body package (a standard "IMP"trapezoidal module, 3 inches high). Electric fields as small as 10-100microvolts/meter and magnetic signals as small as 1-3 milligamma willbe detected.

17. Key Words (Selected by Author(s)) 18. Distribution Statement

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. ofPag.es 22. Price*

Unclassified Unclassified .2 3, 5

*For sale by the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151.

1T

PREFACE

1. OBJECTIVE

The purpose of this report is to summarize the performance of work in

compliance with Article V of Contract NAS5-1l384, entitled "Plasma Wave Ex-

periment for IMP-H," dated February 11, 1971.

The objective of this contract was to provide a scientific instrument

(hardware) for the study of solar wind phenomena on the IMP-H Mission.

Briefly, the work included:

o Development, fabrication, and acceptance testing of one (1)

flight instrument for the Plasma Wave Experiment

o Modification of one (1) GFE-supplied go-no-go test set

o Sustaining engineering, including field support engineering at

GSFC during flight spacecraft integration and testing

o Field support engineering at the Eastern Test Range during pre-

launch and launch activities

o Documentation of all technical aspects pertinent to the design,

fabrication, and test and operation of the instrument and test

set, with specific emphasis on assurance of Instrument-Test Set/

Spacecraft Interface compatibilities.

2. SCOPE OF WORK

In accordance with the contract, this report covers the hardware

(instrument) development, fabrication, integration and testing activities from

contract initiation through launch.

In addition to the discussion of hardware activities, this report also

includes a brief description of the plasma wave instrument and its operation.

Detailed discussion of the scientific theory, its justification, or

results of preliminary post launch data analysis are not within the scope of

work performed under this contract, and are thus not reported herein. (See

Reference 1 for preliminary report on in-flight performance.)

3. CONCLUSIONS

Because much of the TRF/IMP-H instrument utilized components and sub-

assemblies designed and developed for previous TRW plasma wave instruments

(OGO, Pioneer, 0V2-5, etc.), no significant design or fabrication problems

were encountered and work proceeded well. The instrument and GSE were de-

livered to NASA/GSFC on 22 June 1971, and integrated on the IMP-H spacecraft

on 23 June.

The IMP-H spacecraft was launched on 22 September 1972 and, to date,

the instrument has performed quite well.

4. SUMMARY OF RECOMMENDATIONS

Not applicable.

-ii-

TABLE OF CONTENTS

Page

PREFACE........ ... . ............................ i

LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . .... . . Iv

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . .

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . I

1.1 Amplifier Response Time . . . . . . . . . . . . . . 1

1.2 Extended Lower Frequency Limit . . . . . . . . . . . 2

2.0 INSTRUMENT DESCRIPTION . . . . . . . . . . . . . . . . . 2

2.1 General Characteristics . . . . . . . . . . . . . . 2

2.2 Detailed Description . . . . . . . . . . . . . . . . 3

2.3 Summary Characteristics . . . . . . . . . . . . . . 8

3.0 HARDWARE ACTIVITIES . . . . . . . . . . . . . . . . . . 12

3.1 Project Recap . . . . . . . . . . . . . . . . . . . 12

4.0 DESIGN AND DEVELOPMENT CONCEPTS . . . . . . . . . . . . . 12

5.0 FAILURES AND MALFUNCTION . . . . . . . . . . . . . . . . 15

6.0 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . 16

7.0 NEW TECHNOLOGY . . . . . . . . . . . . . . . . . . . . . 16

8.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . 16

-iii-

LIST OF ILLUSTRATIONS

Page

Figure I . . . . . . . . . . .

Figure 2 . .. . . . . .... .

Figure 3 . .. . . . . . ..

Figure ... ....................... ...... 13

- Iv-

LIST OF TABLES

Table 1. IMP-H Plasma Wave Instrument Summary Characteristics - 9Physics & Electrical

Table 2. IMP-H Plasma Wave Instrument Summary Characteristics - 10

Telemetry Command Description

Table 3. IMP-H Plasma Wave Instrument Summary Characteristics - 11

Telemetry Performance Parameters and Outputs

-V-

1.0 INTRODUCTION

The IMP-H instrument payload was originally selected more than five

years before launch, but at a very late stage an opportunity arose to provide

a limited plasma wave instrument. At this late stage, several firm project

and spacecraft restrictions naturally had to be satisfied, and these limita-

tions strongly influenced the instrument design. Specifically, little time

was avilable for overall design and fabrication, and there were firm limits

on weight, power, and other resources. Authorization to start work on the

wave instrument was received on 22 January 1971, and the flight unit had to

be delivered before July 1, 1971; the boom package weight ceiling was 1.25 lbs;

the main body limit was 3.5 lbs; and the power limit was set at 2.5 watts.

With these restrictions in mind, design of the IMP-H plasma wave

instrument was based on the detailed building blocks (automatic gain control

amplifiers, preamplifiers, filters, etc.) that had already been designed for

the OGO-5 plasma wave detector and tested in space since 1968. In fact, some

spare OGO-5 components, such as a magnetic loop antenna, were physically used

in the IMP-H unit without internal modification. The only significant elec-

tronic circuit changes made in going from OGO-5 to IMP-H were those that had

to be imposed because of the differences between the two spacecraft and the

two sets of scientific instrument interface specifications. The major changes

can be summarized as follows:

1.1 Amplifier Response Time

The OGO-5 spacecraft was three-axis stabilized, and it was ap-

propriate to utilize simple amplitude detectors with rise time constants of the

-1-

order of 20 milliseconds and decay time constants of about 400 millisrc ,.ds.

The single most pressing redesign problem involved the need to shorten these

time constants, because IMP-H had a planned spin period near one revolution

per second. Accordingly, most of our redesign activities were devoted to this

problem, and modified IMP-H amplitude detectors used in the VLF channels

(center frequency equal to or greater than 600 Hz) have settling times between

10 and 20 milliseconds.

1.2 Extended Lower Frequency Limit

The IMP-7 spacecraft carries two 1.6 kilobit/second signal en-

coders, one of which was designed for use in a data system test. It was de-

cided that the low frequency plasma wave E or B sensor response could be

transmitted using the data system test encoder, and accordingly a wideband

or waveform channel, covering the frequency range below about 150 Hz, was

added.

2.0 INSTRUMENT DESCRIPTION

2.1 General Characteristics

The IMP-H Plasma Wave Experiment is designed to measure local

electric and magnetic field oscillations over the frequency range 10 Hz to

100 kHz. A 24" electric dipole, a 7" diameter air core search coil, and the

associated preamplifiers are mounted on the counterweight boom. The frequency

range of 10 Hz to 100 kHz for both E and B is processed using an eight-channel

spectrum analyzer. The low frequency range from 10 Hz to 150 Hz is analyzed

by a specially-designed broad active filter channel. The remaining seven

channels utilize high resolution UTC band pass filters to cover the rest of

-2-

the range through 100 kHz. The band pass frequencies are nearly equilly

spaced on a logarithmic scale (actual center frequencies are selected to avoid

known spacecraft interference tones). In the normal mode, the spectrum analy-

zer samples the output from one sensor in a fixed frequency channel for about

one spin period. The other sensor is then sampled for a spin period, and the

analyzer frequency changes every two spins. A complete polarization and fre-

quency scna for both E and B sensors requires approximately 16 spin periods

or twenty seconds. In the snapshot mode, the magnetic sensor is inhibited,

and alternate spins are used for snapshots of our entire set of spectrum

analyzers. The threshold sensitivities are somewhat frequency dependent.

Electric fields as small as 10-100 microvolts/meter and magnetic signals as

small as 1-3 milligamma can be detected.

In addition to the normal data channels discussed above, a low fre-

quency waveform channel and its AGC level duplicating the data coverage of the

low end of the spectrum is provided for an engineering test being made of a

test data system on the IMP-H mission. If this system should operate, very

high. resolution coverage of the range from 10 Hz to 100 Hz will be obtained.

2.2 Detailed Description

The final IMP-H plasma wave instrument characteristics are sum-

marized in Figures I and 2. The top part of Figure I shows the 1.2-pound

boom-mounted package that includes the spare OGO-5 magnetic loop to measure

B-components parallel to the spacecraft spin axis, a 24-inch wire grid elec-

tric dipole (similar to the OGO-5 Q, R, or S antenna; see Reference 2 for

details) to measure E-components in the spacecraft equatorial plane, and the

-3-

1- METER

ELECTRIC DIPOLEMAGNETOMETER

MAGNETIC LOOP

TOP VIEW

IMP-H

Figure 1

-4-

if

II

La

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associated preamplifiers. The bottom part of Figure 1 shows the mounting of

this boom package, as seen from the top of IMP-7.

The wideband E and B signals are processed in the main body package

shown in Figure 2 (with top cover removed). A simplified block diagram for

this unit is shown in the top of Figure 3. The E or B broadband signals are

transmitted to the data system test telemetry as analog waveforms. In addi-

tion, the plasma wave signals are processed by an eight-channel spectrum

analyzer that consists of the automatic gain control (AGC) reading from the

waveform channel, plus amplitude measurements from seven narrowband filter-

fast amplitude detector channels. The instrument has four modes of operation,

because the waveform analyzer and associated AGC reading can be switched to E

or to B, and the seven higher frequency channels in the spectrum analyzer can

independently be used in two modes; that is, the seven upper channels can be

used to obtain either full E and B frequency and polarization scans, or a

succession of E-field spectral snapshots, alternated with E-field polarization

scans in the individual frequency channels.

The individual filter response characteristics are shown in the bottom

panel in Figure 3. The six highest frequency filters are UTC minifilters of

the type used in the OGO-5 detector; the 30 kHz and 70 kHz channels have 30

percent bandwidth, and the filters with center, frequencies at 1.3, 2.3, 5.4,

and 10.5 kHz have 15 percent bandwidths. The broader filter below I kHz is

an active one with center frequency of 500 Hz, effective 45 percent bandwidth,

and 1- db falloff points at 270 and 810 Hz. A steep notch filter at I kHz is

also inserted to minimize any electric field interference that could be as-

sociated with the AC modulation on the MIT Faraday cup plasma probe. The

-6-

ELECTRICDIPOLEANTENNA BROADBAND ANALOG WAVEFORM

E HANNEL DATA TO TELEMETRY

E/B SWITCH COMMANDSCONTROL AND TIMING

EIGHT CHANNEL DATA TO10 Hz - 100 KHz STORAGE REGISTERS

BOOM MOUNTED SPECTRUM ANALYZER AND TELEMETRYPACKAGE

1 kHz NOTCH FILTER

0

-10 -

ATTENUATION

(db)

-20

-30 WAVEFORM

10 102 i03 104 105

FREQUENCY (Hz)

Figure 3

-7-

wide lowest frequency filter is primarily designed to define the limits of the

broadband waveform channel, and it has restricted value as an element of the

spectrum analyzer whose output appears on the conventional scientific encoder-

transmitter data link. In terms of conventional "narrowband" filter charac-

teristics, this lowest frequency or AGC channel on IMP-H has a bandwidth of

67 Hz, and the 10-db falloff points are at 17 Hz and 150 Hz.

The spectrum analyzer output is read out once per 80 milliseconds,

and in the E-B switching mode the format is such that the output from a given

sensor is processed in a fixed-frequency channel long enough for sixteen am-

plitude readings to be transmitted. This 16-point sequence takes 1.28 seconds

and since the spacecraft spin period is just over 1.3 seconds, an individual

sequence lasts for almost one complete revolution of IMP-H, with the plasma

wave instrument in a fixed frequency channel for a given sensor. The E-B

switching mode has sixteen such sequences that make a full spectral and polari-

zation scan, and these sequences are arranged as follows: 70 kHz - E

70 kHz - B - 30 kHz - E - .... 600 Hz - B - AGC - B - AGC - B - 70 kHz - E.

[There is no automatic switching of the 17-150 Hz or AGC channel from E to B,

because this low frequency channel necessarily has a long settling time; the

AGC channel switching is accomplished by ground command only.] The complete

scan thus involves a total of 256 measurements made with two field sensors,

eight frequency channels, and sixteen azimuthal positions of the plasma wave

boom, and it is repeated every 20.5 seconds.

2.3 Summary Characteristics

The "as delivered" characteristics of the instrument are sum-

marized in Tables 1, 2, and 3.-8-

Table I. IMP-H Plasma Wave Instrument SummaryCharacteristics - Physics & Electrical

Main Body Package Weight: 2.9 pounds

Main Body Package Height: 3 inches

Boom-Mounted Package Weight: 1.18 pounds

POWER SUMMARY

Average input: 2.5 watts

Peak input: 2.5 watts

Duty cycle: Continuous

THERMAL RESTRAINTSFacet Card Boom-Mounted Package

Non operating +600C +600C-600 C -60 °c

Operating +500 C +600C-200C -60°C

HUMIDITY RESTRAINTS

Non operating 50% 50%

Operating 50% 50%

High Voltage Operating Restraints: None

Turn-On Operating and Test Temperatures:

+500C +600C-200C -600C

INTERNAL POWER SUPPLIES

Name and Type: DC-DC Power Converter - Magnetic Multivibrator

Voltage: 28 VDC Input± 9 VDC Output+5 VDC Output

Frequency: 20 kHz ± 3%Efficiency: 55%Duty Cycle: 100%

-9-

Table 2. IMP-H Plasma Wave Instrument SummaryCharacteristics - Telemetry CommandDescription

COMMAND OFF: EXPERIMENT POWER OFF

Analog performance parameter I (APP-1) will show 0 VDC

COMMAND ON: EXPERIMENT POWER ON

Analog performance parameter 1 (APP-I) reads converter voltage status

and will have a minimum value of 1.0 VDC

COMMAND 1: LOW FREQUENCY WAVEFORM E/B SWITCH

This command toggles the broadband channel between the E and B modes.

Digital performance parameter I (DPP-1) will indicate the mode.

"l" - +7.75 to +5 VDC - E mode ----- Nominal

"O" - -4 to +0.5 VDC - B mode

COMMAND 2: NARROW BAND a1 INHIBIT SWITCH

This command toggles the narrow band channels between the a

switching of the E and B modes and the aI inhibited or E only

snapshot mode. Digital performance parameter 2 (DPP-2) will indi-

cate the mode.

"I" - +7.75 to +5 VDC - E/B mode ---- Nominal

"0" - -4 to +0.5 VDC - E only snapshot mode

COMMAND R: RESET TO NOMINAL

This command resets the experiment to the nominal modes discussed

above under Command I and Command 2. (After each POWER ON command,

the experiment should be commanded into the mode indicated above

as nominal.)

-10-

Table 3. IMP-H Plasma Wave Instrument SummaryCharacteristics - Telemetry PerformanceParameters and Outputs

DIGITAL PERFORMANCE PARAMETERS

1. E/B SWITCH (DPP-1)

DPP-1 gives the mode of the "low frequency waveform E/B switch."

"l" - +7.75 to +5 VDC - E mode 4-- Nominal

"0" - -4 to +0.5 VDC - B mode

2. A l INHIBIT SWITCH (DPP-2)

DPP-2 gives the mode of the "narrow band al inhibit switch."

"l" - +7.75 to +5 VDC - E/B mode ---- Nominal

"0" - -4 to +0.5 VDC - E only snapshot mode

ANALOG PERFORMANCE PARAMETERS

1. OFF/CONVERTER VOLTS (APP-1)

APP-1 will be at 0 VDC for POWER OFF and will read the converter

voltage for POWER ON. The range of output indicating the state

of health of the power converter will be from a minimum of I VOC

to a maximum of 4.5 VDC.

2. BOOM MOUNTED PACKAGE TEMPERATURE (APP-2)

APP-2 will give the temperature of the boom-mounted package

(thermistor).

ANALYZER CHANNEL OUTPUTS

Eight outputs, O to 5 VDC.

-11-

3.0 HARDWARE ACTIVITIES

3.1 Project Recap

The first formal proposal(1) for the TRW Plasma Wave Experim'nr

(TRF/IMP-H) for the IMP-H mission was submitted on 8 July 1970 to Dr. L.

Kavenaugh of NASA as a substitute for an experiment previously assigned to

Facet 13 on the IMP-H spacecraft. Initially, one flight instrument, one

spare, plus ground support equipment were proposed. Additional requirements

of the IMP project ultimately resulted in two revisions (2 ,'3 ) to the original

proposal.

The contract per Revision 2 of Proposal 17557.000 was negotiated

on 11 February 1971, thus formalizing the start of project activity. In

order to meet the contractual delivery date of I July 1971, however, authori-atin(4)

zation was obtained to begin work on 21 January 1971.

A schedule of the IMP-H Plasma Wave instrument hardware activi-

ties is shown in Figure 4.

4.0 DESIGN AND DEVELOPMENT CONCEPTS

Because of the tight schedule and budget, certain methods and concepts

employed to reduce lead times and costs for the project may be worthy of re-

view here.

From the start, a basic ground rule for the project was that new

design be kept to a minimum. Thus, much of the "design" phase consisted of

merely updating or modifying and re-issuing drawings from previous projects.

In some instances, even spare components "left over" from previous projects

-12-

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were used. Such as the case for the magnetic ("B") field coil (.developed

for the OGO-5 Plasma Wave Detector) which simply required a different con-

nector.

The "minimum new design" concept was probably carried to the ultimate

for the test set (GSE). A test set unit, previously built for the TRW/

Pioneer Electric Field Experiment and no longer in use, was transferred to

and modified for the IMP-H project. While not an original idea, perhaps, the

modification and re-use of otherwise obsolete equipment is possible and, in

this instance, represented a considerable cost savings.

The only item requiring new design was the printed wiring board. As

finally negotiated, the contract called for delivery of only one instrument,

thus posing a problem: with no prototype instrument as a test bed, how was

the integrity of the printed wiring board and component layout to be deter-

mined? The solution to this problem might be called the "Mock Prototype."

Essentially the printed wiring board was procured in two phases. In

Phase 1, a "prototype" board was designed and fabricated. Then all of the

(flight) electronic components (modules, transistors, resistors, etc.) were

attached to the board In their respective places with the exception that the

component leads were not trimmed to length but, rather, left "standing" above

the board on long leads. Thus, it was possible to perform a complete electri-

cal checkout of not only the printed wiring board, but all of the components

and the complete system as well. After the "prototype" board layout was cor-

rected and verified, the artwork changed as necessary, the "flight" board was

ordered and, in final assembly then, all components were transferred to the

flight board -- this time trimming the leads to proper length.

-14-

As it turned out, the "Mock Prototype" not only solved the design

verification problem (two layout errors were found), but also aided in the

parts screening program which was accomplished on the entire "Mock Proto-

type." With all flight components installed, the assembly was exposed to

96 hours (each) at +750 C and -500 C, with system electrical tests preceding

and following each exposure. Thus, the parts were screened as a "system" -

rather than individually - at a considerable saving in costs and time.

5.0 FAILURES AND MALFUNCTION

Except for RFI, the instrument passed all of the required electrical,

magnetic and environmental tests. In the RFI bench test, the instrument

exceeded the specification limits for radiated (magnetic and RF) fields and

for conducted susceptibility portions of the test. Review of this data, the

instrument RFI design, and test methods, however, did not yield any clearcut

direction regarding necessary corrective action. Consequently, resolution

of the RFI problem was deferred until the spacecraft RFI tests were completed.

Results of the spacecraft RFI test, which provided a more representative test

environment for the TRF instrument, indicated that the out-of-specification

conditions would not significantly degrade operation of either the spacecraft

or the instrument. Thus, the instrument was accepted by the IMP Project

Office with no corrective action taken.

Although not a test failure, the fragile "B"-field sensor coil was

inadvertently damaged during spacecraft test and required replacement.

No other test, component, or functional failures were experienced.

-15-

6.0 CONCLUSION

In conclusion, the TRF project was quite successful, modest in scope

and cost and yet, from a cost-effectiveness standpoint, will provide a high

return In scientific value.

7.0 NEW TECHNOLOGY

Because of the "minimum new design" philosophy employed throughout

the project, no new technology was generated under this contract.

8.0 REFERENCES

(1) "A Preliminary Report on IMP-7 Plasma Wave Investigation:

Instrumentation and In-Flight Performance," F. L. Scarf, R. W.

Fredricks, I. M. Green, and G. H. Crook, TRW Systems Group

Technical Report No. 22751-6001-000, March 1973.

(2) Crook, G. H., F. L. Scarf, R. W. Fredricks, I. H. Green, and

P. Lukas, IEEE Trans. Geosci. Elec., GE-7, 2, 120, 1969.

(3) TRW Proposal No. 17557.000, "Proposal for a Plasma Wave Experiment

for IMP-H," dated 26 June 1970 (submitted 8 July 1970).

(4) Revision 1 to TRW Proposal 17557.000, dated 17 September 1970

(submitted 18 September 1970).

(5) Revision 2 to TRW Proposal 17557.000, dated (and submitted)

17 November 1970.

(6) Contract Authorization per "Notice of Work Without Contractual

Coverage," dated 21 January 1971.

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